Ticket vending machines are generally to be found in public places so as to used by anybody.
The vending machine includes a dialog interface enabling a user, during a transaction, to select a ticket which the machine issues in exchange for payment. The payment means used may be coins or bank cards, for example. For this purpose, the machine includes means for receiving the payment means, e.g. a coin mechanism or a bank card reader.
It can happen that a user makes fraudulent use of illegal payment means for paying for the ticket. Such illegal payment means may be forged coins or a stolen bank card, for example.
It is therefore known for the vending machine to include means for detecting illegal payment means, i.e. means for detecting regular payment.
In one known method, when the machine detects that the payment means being used are illegal, the machine refuses the payment. The transaction is thus that the cheat then cannot obtain the desired ticket.
However, the illegal payment means are returned to the cheat who can then reuse them, e.g. with another vending machine. The cheat thus remains anonymous, and is likely to repeat the fraud on a machine that does not have means for detecting the illegal payment means.